When I read the article from the Washington Post relaying that a Department of Homeland Security spokesperson had indicated that Al Qaeda was preparing for more commercial hijackings, I was puzzled... why was this being announced?
It may well have been a move to cut off panic if it was found that they were telling the airlines and security staff without telling the public. It certainly didn't raise the terrorist threat level (yet), but it left me with a bit of a paranoid feeling about Mr. Ashcroft's loss last week of funding for questionable wiretaps.
I know, it's a bit of a stretch, and I hope it isn't correct, but this is the problem with onerous laws like the USA Patriot Act - they leave people wondering what the government is trying to do behind the scenes. Add to that the seeming willingness (and effectiveness) of politicians to try and manipulate public opinion by media stories and the belief by the media that FUD (Fear, Uncertainty and Doubt) sells papers/newscasts/web traffic, and you have a cynics dream.
It may well be that the administration recognizes the fact that September 11th-style hijacking cannot be successful (I pity the fool who tells his fellow passengers that he wants to hijack a plane), as was evidenced that day by the forth plane. As such, they may also feel that alerting the public in a nonchalant manner, without raising the terrorist threat level, will diffuse whatever anxiety may exist, but it still leaves you wondering what they are up to.